Safety latch device



Sept. 29, 1931. c. J. BRISTOL 1,824,866

SAFETY LATCH DEVICE Filed July :50, 1929 Patented Sept. 29, 1931 PATENTfomc CYRUs JQBRISTOLQOF :ons MOINES, IOWA, AssIeNoR To GLOBE ViszrnomrrzeRY & 'SUPPI i` COMPANY, OFDEsMOINEs, rowA, A OORPORATIONOF IOWA- I sArn'rY LATOH Device i,

` LApp1ica''ibn mea July ao, 1929. serial NQ. 352,231.

The plunger typeof lifts has' gone into.` extensive use in connection with'uid pressure lift devicesfor servicing automobiles.

,Inl such devices the automobile is driven 5 onto a platform ldevice when near the ground level, vandthen liu'id pressure is applied to the plunger 'toelevate the auto-' mobile toa point where an operator `may conveniently and easily service the'- under part of theautomobile. l v The object of my inventionis to provide a safety latch device of simple, durableand inexpensive constructionand4 so arranged that it will automatically under all conditions lock the plunger against downward movement until the operator-manually releases the latchfdevice.

More specifically it is myobject to provide aV latch deviceof this general character in which, when the safety latch device has once been manually released by the Operator andk the plunger lowered either Ya slight distance orga fullstroke, andthe plunger again elevated, the latch device will automatically hold the `plunger in its elevated position without any `attention on vthe part of the operator.` l Y `My invention consists in theconstruction, arrangement and-combination of the-.va-

rious parts of the device i* wherebythehobl jects contemplated'are attained, as V,hereinafter more fully set forth, pointed. out in my claims, andillustrated inthe accompanying drawings, -in'whichz f Y Figure 1 shows a side elevation partly in section illustrating a vconventional type cyl-` inder and plunger having my improved latch device applied thereto, the plunger bein shown in its elevated position. Y AFigure 2 shows an enlarged,'detail, sectional view of a--portion- ,of vthe plunger, the upper portion `of the cylinder `and my improved latch device `applied thereto and shown in positionfor locking the plunger "153 against" downward movement. The dotted lines in this figure illustrate the ,position of the parts when'the operator has manually operated the latch device to permit the plunger to descend.' f

.5Q Figure 3 shows a similar view with the latch device inl position *wherethelatch bars engage'theguidefflange at the top of the cylinder,'and in this figurethe dottedlines-showthe position of the latch devicewhen thelatch bars are below the guide flange yat the-'top ofthe cylinder.

Figure l is ay detail sectional view Von the vline l-fl of -Figure 2.

Referring vto the accompanying dra-wings `I havefusedftliev referenceY numeral l0 vto indicate generally a cylinder ofthe type now commonly used in automobile lifts. At the top of thelcylinder there is a guide flange 11 firmly secured to the cylinder by a bolt 12 and nut 13. It will be noted upon reference 'to 'Figurel 2 that the cylinder Y fixed tothe outer surface of the guide flange' 11 and thatfhence the innercylindrical sur-l face of theguide flange is of considerably less diameter'than that of the" interior of the cylinder 10 below the guide flange.

The plunger is indicated generally by the reference numeral 514 and forms Va close sliding fit with the interior of the guide flange V11, and has'at its lower end-a customaryyielding packing15.*'-`

My 'improved latch deviceis permanently *securedy nearthe bottom of the plunger by two parallelqsupporting bars '16,"spaced apart 1 fromt eachother and extended trans? versely acrossf the 'interiorof-the plunger and firmly fixed, preferablyfby spotV weld-V ing, Yto the interior of thev plunger. j

f These supporting bars 16 'are each provided with slots17 near their ends. Pivotally mounted upon the supporting bars 16 are levers 18,'each having-a fulcrum pin 19 extended through it and through theslots' 17. 4-These'levers are arranged in pairs lone pair on, each end of the 'bar 16. j' Pivotally mounted between the upper ends of each pair of-leverslS are the'latch bolts20, their outer ends being beveled downwardly' and outwardly. These latchl bolts are extended through round openings'in the Aplunger walls. i Pivoted to the lower end of each pair.' of

levers y18 is a link 21.` The inner ends of these links are pivotall'y connected to each other and toa verticallyl movabletrip bar 22, which is slidingly mounted at its upper end in a cross piece 28 fixed to the plunger, which trip bar 22 has a slot 24 formed therein through which there is extended a pin 25 fixed to the stationary cross p iece 16 to lloimit the up and down movement ofthe trip One of the fulcrum pins 19 has p ivotedto pin 19 has a metal the rod 26 is an expansible coilspring 2 8 to normally hold the pivot pins19-at their outer limits of movementin theslot-s 17..

There is a similar rod 26 and spring 28 for eaehgsidevof the latch device.

Each pair o flevers 18 .is provided with a fulcru'm-pin 29 mountedbetween the levers and pivotally Connected to them by alpin 30. ,These fuleruml pinsj29- are projected horizontally outwardly .through openings formed in the wallsof the plunger and A.their outer ends are inclined. downwardly and outwardly. v

In practical operation and assumingthat the -trip bar` 22 is .at its lower limit. ofmove ment,.as shownhy solid lines in Figure 2,- thenfthe levers 18 areheld by the links 21. imposition .with thebolts20'at their outer. limits of. movement, the pivot points ofthe leversl- 18 -under sueli circumstances being. on tlne-pive't'pinsli- Hence, thevveight of the parts alone. without any spring action will always hold thebolts-,20 outwardly and pre= vent ay downwardl mt'lvementV of thel `plunger fromvits elevated position.. Y

Furthermore; and assuming vthat the. latch deviceon theplunger iselevated above the flange 11,-.thenfevenif the operator. should elevate the tripban- 22 and releasel it, the latchbolts 20 would still.y remain 'in` an ex,- tended position. However, under. the same circumstances, and assuming that/the. operator raised the trip bar and held it` up, then thegfulorumpins 29 wouldproject outwardly far enbugh to. prevent; the latchdeviceffrom n 'ioving4 downwardly past the flange l1. This position: is shownl by dotted lines in Fig; S Inf thisrfigure these fulcrum pins are shown below the flange. 11', but it will be seen that ifabove the flange l11 they would prevent downward movement. of the plunger. Hence, vno manipulation; of any-kind of they trip bar 22. e'an haveanyeffeotupon theflatch 'device,` unless: and, until theA latch devi'ee. is-in. its normal position supporting the plunger in elevated pos-itiomjasshown by solid linesinFigure 2. VVVhen in this position, and assuming that the operator d ee sires to lower the plunger, then the.- trip bar -225is raised andthis, as `shown lby f dotted linesv in Figure- 2, will Cause the fulerum pins 29 to engage the inner surface of the flange 11, and therebyl cause; these pins` 2.9

dead center, as@ showniby dottedlnes: inV

Figure 2. Henee-Ytheoperator need only elevate the trip bar 22, and then may let go of itA and the parts will remain `in the positionfshown by. `dotted lines in Figure 2 until such'time as tlie operator is ready to raise or lower. the plunger-,-

If: theoperator infintending to. lower the plungershouldY accidentally raise it for a.

slight1 distance,l thenv so long as the fulcrum pins 29 are in engagement with-the.flange-11` the parts-will alLremain in the same position andI the plunger can be raised, say for instanee,.an inch, and then lowered, but ifthe oprator should raise the *plungerl far enough for the fulcrum pins 29.*to clear the top of. the flangey 11, then. the trip bar 22 will droplby gravity andthe parts will assume the position. shownby'solid lines-in Figure 2; andthe plunger couldnot be lovvered'until the ltrip vbar was againmanipulated;

Assuming, however, thatvthe operator lowers the plunger, then so-.longgas the latch bars 20 are in engagementA with the inner surface of the flange- 11,.the'parts will; all remain infthesame positionas that shown by dottedlinesinlFigure12, andfby solidlines in Figure 3i When; however, the latchbars 20 passi-below. the flange-11, then alli ten sion of the'springisV 28-.isrelieved andthe trip bar 22 willdrop yby gravity to thefposi-v tionshown by dotted lines-in Figuregand all of the latch bars and pivot pins Vwill be relievedk of. any spring tension and.v the,

plunger mayv freely'move up` ancldowny in the cylinder.. Then when the plunger is again elevated, the inclined faces of thev latch: bars 2.0 will' cause. themA to movei'n= wardly past the' flange; 11, and Whenathey get above it. they willagainbe movedv out-e warrlly to the positionshoWn-by solidilines Ain Figuren Withmy improved devicathexefore, it is pratically impossible fr a Careless operator to permit theplunger to drop, because there is only one position in which' apull uponthetrip bar 22 will have any eil'ect, and that is the position shown by solidlines inA Figure 2, and then the Operator must raise the plunger slightly until the latch bars clear. the top of' the. ,flange and vthe fulcrumpins engage the. interior of, the flange. It is. only when the parts are in said position that a pull upon the tripbar will permita lowering of the-plunger.4

I claim as my invention:

l. In a safety latch device, the combina'- tion of a plunger, a flange through which the plunger is slidingly extended, a support carried by the plunger, a lever pivot-ally and slidingly mounted on the support, a latch bar pivoted to the lever on one side of c the support, a fulcrum pin pivoted to the lever on the opposite side of the support, a spring for normally holding the lever at its outer limit of movement relative Ato its support, said parts being so shaped and proportioned that when the fulcrumpin engages said flange the latch bar will be held outwardly to engage the top of said flange and thereby prevent the downward movementof the plunger, and manually operated means for compressing the spring and withdrawing the latch bar.

2. In a safety latch device, the combination of a plunger, a cylinder in which the plunger is slidingly mounted, a guide flange at the top of the cylinder and through which the plunger is slidingly extended, said flange being projected inwardly farther than the interior of the cylinder, a support fixed to the plunger, two pairs of levers pivotally and slidingly connected to said supports, a latch bar pivoted to the upper end of each pair of levers and extended outwardly through the plunger, a fulcrum bar pivotally mounted between each pair of levers below the support and extended outwardly through the sides of the plunger, a link pivotally connected tothe lower end of Veach pair of levers, a trip bar slidably supported within the plunger and pivotally connected at its lower end with said links, and a yield-r ing pressure device for exerting an outward pressure upon theV pivotal connections between said levers and the said support, for the purposes stated.

3. In a safety latch device, the combination of a hollow plunger, a lever pivotally supported within the hollow plunger, a latch bar carried by the lever at one side of its fulcrum and extended outwardly through the plunger, a fulcrum pin connected to the lever on the side of its fulcrum opposite from the latch bar a-nd projected outwardly through the plunger, means for normally holding the lever in position with the latch bar projected outwardly, a flange arranged in the path of the fulcrum pin for forcing it inwardly when the plunger moves upwardly past the flange bar to its withdrawn position, and manually operated means for withdrawing` thelatch bar.

4. The combination in an automobile lift of an upright cylinder, a hollow piston rod closed at its lower end, a packing device on the lower end of the piston rod to form a seal between the lower end of the piston rod and the interior of the cylinder to prevent the entrance ofthe piston operating fluid above the lower end of the piston, a latch device supported within the hollow -pistoir rod, `the piston rod being formed with an opening through which the latch may project outwardly to engage and rest upon a stationary part at the upper portion of the cylinder when vated position, and manually operated means connected with the latch and extended upwardly through the hollow piston rod for withdrawing the latch from its position projected beyond the piston rod.

5. In a fluid pressure automobile lift, the combination of a cylinder,a hollow piston rod slidinglyl mounted in the cylinder having its lower end closed, means for forming end of the piston and the interior of the cylinder, a latch device mounted within thev hollow piston, the piston being formed with a slot through which the latch may be projected outwardly through the piston to position where it will engage a stationary part at the upper portion ofthe cylinder when lowered, and means for forcing the latch inwardly to permit the piston to be lowered below the upper end of the cylinder.

' Des' Moines, Iowa, July 26, 1929.

CYRUS J. BRISTOL.

the piston rod is in an ele-V -a fluid-tight connection between the lower 

